VEGF up-regulation by G93A superoxide dismutase and the role of malate-aspartate shuttle inhibition

A gain of interaction of the amyotrophic lateral sclerosis (ALS)-linked G93A-superoxide dismutase-1 (G93A-hSOD1) with cytosolic malate dehydrogenase (cytMDH), a key enzyme in the malate-aspartate shuttle, diverts neurons towards anaerobic metabolism. Changes in vascular endothelial growth factor (VEGF) are reported in ALS and hypoxia. Here we report that expression of G93A-hSOD1 fused with green fluorescent protein in NSC-34 cells enhanced VEGF expression and levels of VEGF and its upstream regulator hypoxia-inducible factor (HIF-1α). G93A-hSOD1 expressing cells were unable to further up-regulated VEGF in response to Co²⁺ and H₂O₂. Amino-oxyacetate that inhibits the malate-aspartate shuttle caused a similar increase in VEGF mRNA and impaired response to H₂O₂ in WT-hSOD1 expressing cells. Interruption of the G93A-hSOD1/cytMDH interaction reduced VEGF expression in G93A-hSOD1 expressing cells and restored their ability to up-regulate VEGF in response to Co²⁺ and H₂O₂. These results demonstrate that the ALS-linked G93A hSOD1 mutation impairs VEGF regulation compatible with the inhibition of neuronal malate-aspartate shuttle.